Foreign exchange – inventory

Hi,

Below is the question:

Goods were purchased for Dinar 80 million cash when the exchange rate was $1:Dinar 5Moyes had not managed to sell the goods at 30 20X8 and the net value at that date was to be Dinar 60 million. The exchange rate at this date was $1:Dinar 6The inventory has been valued at 30 September 20X8 with the loss resulting from both the exchange and correctly included within cost of sales.

Sir, I did not understand how did a foreign exchange loss arise?

Thanks in advance!